The IRS clobbered Robert De Niro with a $6.4 million tax lien, documents show.

The two-time Oscar winner learned of the massive lien from news accounts on Thursday, his spokesman insisted, adding that the actor had a check for the full amount hand-delivered by day’s end to the feds in New York.

The embarrassing notice was filed with the city Department of Finance on Feb. 3 against De Niro’s multimillion-dollar Tribeca investment property at 114 Hudson St.

The IRS first put De Niro on notice about his 2013 personal-income tax arrears three months ago, according to a legal source who spoke on condition of anonymity.

But the warnings that a lien loomed, and ultimately the lien document itself, had all been mailed to 114 Hudson St., not his home address, the source said.

De Niro and his wife, Grace Hightower, live on Central Park West in a $125,000-a-month rental, one of the city’s priciest.

When news broke of the lien — which totaled $6,410,449.20 — De Niro sent his small army of accountants and lawyers into action to pay the bill.